1. Technical Field
The present invention relates generally to condition monitoring systems and, more particularly, to a system that monitors air pressure in the tires of a motor vehicle, and that generates a signal indicative of the tire pressure in each of the tires to improve tire life, minimize tire wear, and increase vehicle performance and safety.
2. Discussion
Correct tire pressure is a critical factor in the safe operation and performance of a motor vehicle. Overinflated tires often result in unnecessary tire wear and less than optimal vehicle performance. Under inflated tires typically result in increased tire wear, decreased vehicle performance, and compromise the ability of the tires to maintain a safe interface with the road.
Conventionally, tire air pressure has been checked with mechanical gauges designed to be inserted over tire inner tube valve stems. Such gauges provide a generally accurate air pressure reading. However, the gauges are incapable of providing continuous monitoring of the air pressure within the tires and are limited in accuracy, and also require a driver concerned about tire air pressure to physically stop and exit the vehicle to check the tire pressure. In addition, such mechanical gauges do not provide any warning indication when the tire pressure reaches a level considered to be dangerous or unsuitable (such as below 14 psi in a typical passenger motor vehicle) for normal driving conditions.
Other systems utilize an active inductor capacitor (LC) circuit affixed within the tire to monitor tire air pressure. However, the active LC circuit requires a power source for operation. Because it is mounted within the tire, the power source, as well as the additional circuit components, are subjected to rotational vibration and other extreme conditions caused by temperature fluctuation. The circuit components are also difficult to install and replace if damaged or depleted due to their location within the tire. In addition, such systems typically provide no warning to the driver when the tire pressure falls below or rises above a certain minimum/maximum acceptable level.
What is needed then is a tire pressure sensing system which does not suffer from the above-mentioned disadvantages. This, in turn, will provide a sensing system which monitors tire air pressure using a passive sensor, provides improved mounting of the sensor within the tire, provides a system which is less susceptible to interference, provides a sensor system which can accurately monitor the change in tire air pressure, and provides improved sensors which operate to identify if the tire air pressure is outside a pre-determined range or identifies the actual tire air pressure based upon variable capacitance or inductive changes. It is, therefore, an object of the present invention to provide such a tire pressure sensing system.